title: QTc interval and electrocardiographic changes by type of shift work.
abstract: BACKGROUND
  We conducted a cross sectional survey of electrocardiographic changes among shift-workers.
  
  
  METHODS
  We classified the electrocardiogram morphology, and measured the QTc interval in 91 male workers engaged in regular daily work-shifts, 32 in 24 hr work-shift (h24), and 93 in irregular 6 hr work-shift (h6).
  
  
  RESULTS
  With reference to daily workers, the QTc interval was prolonged among h6 workers (P < 0.001) and h24 workers (P < 0.005). The age- and obesity-adjusted standardized prevalence ratio (SPR) of a borderline/prolonged QTc was 2.2-fold among h6 workers (95% CI 1.2, 4.2); conduction disorders (SPR = 2.6; 95% CI 1.3, 5.2) and repolarization disorders (SPR = 1.9; 95% CI 1.0, 3.5) were also more frequently observed among h6 workers. Excluding 19 subjects with risk factors for prolonged QTc did not change the results.
  
  
  CONCLUSIONS
  Our study reveals significant changes in the ECG morphology in relation to shift-work, especially in unpredictable and non-standard working hours.
authors.affiliation: Department of Public Health, Clinical and Molecular Medicine, Occupational Health Section, University of Cagliari, Monserrato (Cagliari), Italy. melonim@medicina.unica.it
authors.forename: Michele
authors.initials: M
authors.lastname: Meloni
authors.forename: Davide
authors.initials: D
authors.lastname: Setzu
authors.forename: Alberto
authors.initials: A
authors.lastname: Del Rio
authors.forename: Marcello
authors.initials: M
authors.lastname: Campagna
authors.forename: Pierluigi
authors.initials: P
authors.lastname: Cocco
mesh_terms: D000328:Adult; D001145:Arrhythmias, Cardiac / Q000453:epidemiology / Q000503:physiopathology; D003430:Cross-Sectional Studies; D004562:Electrocardiography; D006329:Heart Conduction System / Q000502:physiology*; D006801:Humans; D008133:Long QT Syndrome / Q000453:epidemiology / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000453:epidemiology; D014940:Work Schedule Tolerance / Q000502:physiology*; D055815:Young Adult
keywords: QTc interval; electrocardiogram; shift work